Best answer by Ed_OVO
You pay for your energy in advanced, so the Direct Debit that is coming out on the 22nd will pay for the end of may/Junes usage. You'll notice that when you first switched over to us, you'll have had a Direct Debit taken very soon after.
We do this so that we can more accurately buy energy, saving us money, which we can then pass on through lower unit rates to our customers.
You can of course change the billing date or Direct Debit date, so that the payment comes out before the statement's generated. You'd just need to contact us at email@example.com and we'll get that changed for you.